1. Field of the Invention
The present invention relates to a lubricating structure for an internal combustion engine and, more particularly, to an improvement of lubricating ability on an inner face of a cylinder liner.
2. Description of the Related Art
Generally, lubricating oil in the internal combustion engine is sucked up from an oil pan through the intermediary of a strainer by an oil pump. Thereafter, the pressure of lubricating oil is controlled by a pressure governor and subsequently, the oil is fed to a main gallery. Formed to branch off from the main gallery are respective oil holes (or lubricant passages) through which the lubricating oil is supplied to respective lubricating sections, for example, a moving valve system, the crankshaft and so on.
Hereat, the lubricating oil for each lubricating section of the crankshaft is firstly fed from the main gallery to a main journal and sequentially fed to a pin journal through an oil hole (passage) penetrating both crankshaft and crank pin and finally reaching the crank pin. Thereafter, the lubricating oil is drained into an oil pan through a clearance between the main journal and the crankshaft and another clearance between the pin journal and the crank pin. While, the lubricating oil brought to each pin journal passes through a splash oil hole having one end opening at the inner face of a circular hole for bearing the crank pin of the pin journal and the other end opening at a base of a connecting-rod as a lubricant injection nozzle. Next, on completion of the piston lubrication, the lubricating oil is returned to the oil pan.
Here, regarding the formation of both splash oil hole of the connecting-rod and oil hole penetrating the crankshaft for the pin journal, there is a known lubricating structure where the arrangement of both holes are established such that, when the position of the former oil hole coincides with the position of the latter hole, then the lubricating oil ejected from the splash oil hole is supplied against the inner face of the cylinder liner (see Japanese Unexamined Patent Publication No. 9-280027).
However, since the above-mentioned earlier art has been provided on only consideration to coincide the position of the splash oil hole with the position of the oil hole of the pin journal when the splash oil hole faces to the inner face of the cylinder liner, there is not defined a positional relationship between the oil hole in the main journal communicating with the main gallery and the oil hole formed in the crankshaft. That is, even when the position of the splash oil hole agrees with the position of the oil hole of the pin journal, the position of the oil hole on the main journal's side does not coincide with that of the oil hole formed in the crankshaft.
Therefore, the lubricating oil, which has been supplied from the oil hole of the main journal at the positional incidence between the splash oil hole and the oil hole of the pin journal, is introduced into the oil hole of the crankshaft through a groove section between the crankshaft and the main journal.
In such a lubricating route, due to a great reduction in lubricant pressure at the groove section between the crankshaft and the main journal, it is not possible to ensure a sufficient amount of lubricant ejected from the splash oil hole via the oil hole of the crankshaft and the sequential oil hole of the crank pin. Especially, since the lubrication on the inner face of the cylinder liner is insufficient at the vehicle's cold starting, the earlier art lubricating structure cannot perform sufficient effect to reduce the piston slap.